The French vehicle testing authorities examine import cars before registration in France...

The DREAL (Directions Régionales de l’Environnement, de l’Aménagement et du Logement) replaces the DRIRE (Directions Régionales de l’Industrie, de la Recherche et de l’Environnement). DREAL is the authority responsible for vehicle testing imported cars before they can be registered in France.
Go in person to the DREAL.

A copy of the certificate of purchase and customs clearance certificate (issued by the Centre des Impots)

Driving licence

Cheque book to pay the fee

The vehicle will be inspected and verified that the make, year and chassis number correspond to French homologation standards, la fiche d'homologation. This process can take two or three weeks. If the car conforms to these standards, there will be a fee to pay, varying on the vehicle.
Note: Even if the vehicle is homogene, there are certain things that may need changing because, for example the engine you have does not have the same number as the one in the French homologation fiche, or the optics are not the same, meaning the headlight casings of a right hand drive car will need to be reset or replaced to accommodate driving on the left.
It may therefore be required that changes are made and the vehicle be returned to the DREAL to be re-inspected and approved. The vehicle may be driven in the interim.